1. Field of Invention
An embodiment of the invention relates generally to the field of integrated circuit packages, and more specifically to methods and apparatuses for creating multilayer integrated circuits packages.
One type of integrated circuit package is known in the art as a multi-chip module (MCM) and has a composite multilayered structure including conductive and nonconductive regions that are used to form wiring or circuit lines to connect to semiconductor devices such as very large scale integrated (VLSI) chips and/or discrete circuit elements, etc.
2. Art Background
Integrated circuit packages are currently made using various multistep processes. The cost to produce the integrated circuit package increases as the number of steps increase that are required to complete the integrated circuit package. Currently, the basic process used for processing an organic substrate such as epoxy follows a series of serial steps. For example, the epoxy substrate is laminated to a copper sheet. Photo resist is applied to the copper sheet. The desired circuit pattern is exposed on the copper using a photo tool. The photo resist is developed to form a photo resist mask and the copper layer is etched in alignment with the photo resist mask, leaving a circuit trace of copper attached to the underlying epoxy substrate in the regions unprotected by the photo resist mask. The photo resist is stripped and the assembly is cleaned.
Through holes are made in the substrate by mechanical or laser drilling. The through holes are cleaned and filled with metal to provide vias within the substrate. Present processes, as described above, require separate steps to form the copper trace and the vias, thereby increasing the cost to produce the finished circuit package. Creation of circuit traces of different depth also requires separate steps since it will be necessary to apply, cure, and remove photo resist for each depth of copper created. Thus, the cost to produce multilayer integrated circuit packages increases rapidly as the complexity of the combined circuit increases.
Current methods of creating vias, such as mechanical or laser drilling, result in the need for pads, vias cannot be placed directly in the copper traces themselves. Thus, circuit board area is wasted due to the need to allocate space to the via for use as a pad.
The previous description of processing an organic substrate such as epoxy would be similar for ceramic or another material. Serial separate steps are required to form the vias and circuit traces on the substrate, which lead to increased cost and lower overall reliability.